This invention relates to scheduling of terminals in wireless communication systems, and in particular but not only, to a scheduling metric which may be efficiently calculated for terminals in a mobile radio system.
A wireless communication system is usually configured to balance efficient utilisation of the wireless medium with acceptable quality of service for users. A scheduler is provided to implement this balance. Ideally the scheduler would assign multiple users to a single resource, which produces a linear increase in utilisation. However, interference between an increasing number of users will degrade service quality to some extent.
A scheduler may use a fixed or statistical estimation of quality as a metric when allocating resources to users in a multiuser system, such as signal to interference levels or bit error rates for example. The scheduler receives data relating to the user terminals, from base stations in the system, and attempts to determine which groups of terminals are best allowed to transmit simultaneously during an interval of time or radio frequency.
The terminals in these wireless systems may use a wide range of communication protocols. They may be narrowband transmitters for example, operating within a 12.5 kHz channel such as provided in P25 APCO, DMR or analogue radio, or operating within a 6.25 kHz channel as provided in dPMR. Alternatively they may be relatively wideband transmitters using one or more 180 kHz resource blocks as provided in LTE. Scheduling of terminals using a mixture of protocols such as LTE and P25 may also be required.